Erosion Resistant Subterranean Drill Bits Having Infiltrated Metal Matrix Bodies

ABSTRACT

Subterranean drill bits having good erosion resistance, strength, toughness, and thermal stability are disclosed. The drill bits comprise a bit body carrying at least one cutting element and having an infiltrated metal matrix. The infiltrated metal matrix comprises a matrix powder composition bound together by an infiltrant. The matrix powder mixture includes cast tungsten carbide powder having a particle size of −30 (600 micron) +140 mesh (106 micron), a second component powder consisting of one or more other types of tungsten carbide particles, and a metal powder.

FIELD OF INVENTION

The present invention relates to subterranean drill bits. Morespecifically, the present invention relates to subterranean drill bitscomprising at least one cutting element and an infiltrated metal matrix.

BACKGROUND OF THE INVENTION

It is well-known to use in subterranean applications such as mining anddrilling drill bits, e.g., for gas and oil drilling, having bit bodiesor portions thereof which comprise an infiltrated metal matrix. Such bitbodies typically comprise one or more cutting elements, such aspolycrystalline diamond cutting inserts, embedded in or otherwisecarried by the infiltrated metal matrix. The bit bodies are typicallyformed by positioning the cutting elements within a graphite mold,filling the mold with a matrix powder mixture, and then infiltrating thematrix powder mixture with an infiltrant metal.

The following patents and published patent applications pertain to ordisclose an infiltrated matrix powder useful for forming subterraneandrill bit bodies: U.S. Pat. No. 6,984,454 B2 to Majagi, U.S. Pat. No.5,589,268 to Kelley et al., U.S. Pat. No. 5,733,649 to Kelley et al.,U.S. Pat. No. 5,733,664 to Kelley et al., U.S. Patent ApplicationPublication No. 2008/0289880 A1 of Majagi et al., U.S. PatentApplication Publication No. 2007/0277646 A1 of Terry et al., all ofwhich are assigned to the assignee of the present patent application.The following patents and published applications also pertain to ordisclose an infiltrant matrix powder for bit bodies: U.S. Pat. No.7,475,743 B2 to Liang et al., U.S. Pat. No. 7,398,840 B2 to Ladi et al.,U.S. Pat. No. 7,350,599 B2 to Lockwood et al., U.S. Pat. No. 7,250,069B2 to Kembaiyan et al., U.S. Pat. No. 6,682,580 to Findeisen et al.,U.S. Pat. No. 6,287,360 B1 to Kembaiyan et al., U.S. Pat. No. 5,662,183to Fang, U.S. Patent Application Pubication No. 2008/0017421 A1 ofLockwood, U.S. Patent Application Publication No. 2007/0240910 A1 ofKembaiyan et al., and U.S. Patent Application Publication No.2004/0245024 A1 of Kembaiyan.

A look at a few of these patents and published patent applications willhelp the reader to understand the state of the art. U.S. PatentApplication Publication No. 2007/0240910 A1 discloses a composition forforming a matrix body which includes spherical sintered tungsten carbideand an infiltration binder including one or more metals or alloys. Thecomposition may also include cast tungsten carbide and/or carburizedtungsten carbide. The amount of sintered spherical tungsten carbide inthe composition preferably is in the range of about 30 to about 90weight percent. Spherical or crushed cast carbide, when used, maycomprise 15 to 50 weight percent of the composition and the carburizedtungsten carbide, when used, may comprise about 5 to 30 weight percentof the composition. The composition may also include about 1 to 12weight percent of one or more metal powders selected from the groupconsisting of nickel, iron, cobalt, and other Group VIIIB metals andalloys thereof.

U.S. Pat. No. 7,475,743 B2 discloses a subterranean drill bit thatincludes a bit body formed from an infiltrated metal matrix powderwherein the matrix powder mixture includes stoichiometric tungstencarbide particles, cemented tungsten carbide particles, cast tungstencarbide particles, and a metal powder. The stoichiometric tungstencarbide particles may have a particle size of −325 (45 micron) +625 mesh(20 micron) and comprise up to 30 weight percent of the matrix powder.The cemented tungsten carbide particles may have a particle size of −170(90 micron) +625 mesh (20 micron) and account for up to 40 weightpercent of the matrix powder. The cast tungsten carbide may have aparticle size of −60 (250 micron) +325 mesh (45 micron) and account forup to 60 weight percent of the matrix powder. The metal powder mayaccount for between 1 and 15 weight percent of the matrix powder and mayinclude one or more of nickel, iron, cobalt, and other Group VIIIBmetals and alloys thereof.

U.S. Pat. No. 6,682,580 B2 discloses matrix powder mixtures which may beused for producing bodies or components for wear-resistant applicationssuch as drill bits. The matrix powder mixtures contain spheroidal hardmaterial particles having a particle size of less than 500 microns, andpreferably in the range of between 20 to 250 microns. The spheroidalhard material particles comprise between about 5 and 100 weight percentof the matrix powder. The matrix powder may also include block hardmaterials in the size range of between 3 and 250 microns and in the formof crushed carbides or metal powder. These block hard materials functionas spacers between the spherical hard material particles to aid in theinfiltration of the matrix powder. The spherical hard particles may bespheroidal carbides and are preferably spheroidal cast tungsten carbide.They also may be dense sintered cemented tungsten powders with a closedporosity or pore-free sintered cemented tungsten carbide pellets. Thespheroidal carbides also may be carbides of the metals in the groupconsisting of tungsten, chromium, molybdenum, vanadium, and titanium.The metal powder may comprise between about 1 to 12 weight percent ofthe matrix powder and be selected from the group consisting of cobalt,nickel, chromium, tungsten, copper, and alloys and mixtures thereof.

U.S. Pat. No. 5,733,664 also discloses matrix powder mixtures suitableto be infiltrated to form wear element bodies or components forwear-resistant applications such as drill bits. The matrix powdermixtures include crushed sintered cemented tungsten carbide particles,wherein a binder metal comprises between about 5 and 20 weight percentof the cemented tungsten carbide composition. The crushed sinteredcemented tungsten carbide powder may account for 50 to 100 weightpercent of the matrix powder and have a particle size of −80 (180micron) +400 mesh (38 micron). The matrix powder mixture may alsoinclude up to 24 weight percent of cast tungsten carbide having aparticle size of −270 mesh (53 micron) with superfines removed; up to 50weight percent tungsten carbide particles having a particle size of −80(180 micron) +325 mesh (45 micron); and between about 0.5 and 1.5 weightpercent of iron having an average particle size of 3−5 microns.

Although these earlier infiltrated metal matrices have performed in asatisfactory fashion, there is still an unfilled need for subterraneandrill bit bodies for particular applications which require infiltratedmetal matrices having a combination of good erosion resistance,reasonable strength, and good thermal stability. The present inventionaddresses that unfilled need.

SUMMARY OF THE INVENTION

The present invention provides subterranean drill bits comprising atleast one cutting element carried by a bit body having the desiredcombination of good erosion resistance, reasonable strength, and goodthermal stability. The bit body comprises an infiltrated metal matrixwhich includes an infiltrant and a metal powder mixture. The metalpowder mixture comprises about 30 to 90 weight percent of a firstcomponent powder, about 10 to 70 weight percent of a second componentpowder, and up to about 12 weight percent of a third component powder.The first component powder consists of particles of cast tungstencarbide of +140 mesh (106 micron) particle size. At least 15 weightpercent of the matrix powder mixture consists of first component powderparticles having a particle size of +100 mesh (150 microns) and thematrix powder mixture contains substantially no particles of the firstcomponent powder which are less than 140 mesh (106 micron) in particlesize. The second component powder consists of particles of at least oneselected from the group consisting of macrocrystalline tungsten carbide,carburized tungsten carbide, and cemented tungsten carbide. The thirdcomponent powder consists of particles of a metal selected from thegroup of at least one selected from the group consisting of transitionmetals, main group metals, and alloys and combinations thereof.

The particle size distribution of second component powder is selected sothat these particles fit in among the cast carbide particles in a mannerso as to enhance the thermal stability, toughness, and strength of thedrill bit body. Preferably, the particle size of the second componentpowder is less than 80 mesh (177 micron).

Accordingly, one aspect of the present invention relates to subterraneandrill bits comprising at least one cutting element for engaging aformation being carried by such infiltrated metal matrix bit bodies.

Another aspect of the present invention relates to matrix powdermixtures for making such infiltrated metal matrix bit bodies.

BRIEF DESCRIPTION OF THE DRAWINGS

The criticality of the features and merits of the present invention willbe better understood by reference to the attached drawings. It is to beunderstood, however, that the drawings are designed for the purpose ofillustration only and not as definitions of the limits of the presentinvention.

FIG. 1 is a schematic view of an assembly used to make a subterraneandrill bit according to an embodiment of the present invention.

FIG. 2 is a schematic view of an assembly used to make a subterraneandrill bit according to another embodiment of the present invention.

FIG. 3 is an isometric view of a subterranean drill bit according to anembodiment of the present invention.

FIG. 3A is an isometric view of a subterranean drill bit according toanother embodiment of the present invention.

FIG. 4 is a photomicrograph of the microstructure of an infiltratedmetal matrix according to an embodiment of the present invention.

FIG. 5, which shows a plot of the transverse rupture strength versus theerosion resistance data from Table 3, wherein the results of theexamples of the present invention are indicated by diamond markers whilethose of the comparative samples are indicated by square markers.

DESCRIPTION OF PREFERRED EMBODIMENTS

In this section, some preferred embodiments of the present invention aredescribed in detail sufficient for one skilled in the art to practicethe present invention. It is to be understood, however, that the factthat a limited number of preferred embodiments are described herein doesnot in any way limit the scope of the present invention as set forth inthe appended claims.

Inasmuch as an important aspect of the present invention is the particlesize of the various powder components of the matrix powders which areused to form the subterranean drill bit bodies, it is necessary to havea means for describing those particle sizes. Mesh size is a convenientmeans for describing the particle sizes of a powder and is used hereinfor that purpose with regard to the description of the presentinvention. Mesh sizes are also sometimes called “sieve sizes” or “screensizes.” The numerical portion of the mesh size refers to the number ofsquare openings there are per lineal inch (2.54 cm) of the mesh taken ina direction parallel to the sides of the square openings. For example,100 mesh refers to a mesh having 100 openings per lineal inch (2.54 cm).Since the length of a side of an opening in the mesh depends on thethickness of the filaments that make up the mesh, various standards havebeen adopted to govern the filament thickness, and, thereby, side lengthof the openings. Mesh sizes based upon ASTM Standard E 11-70 (1995),i.e., U.S. mesh sizes, are used herein. To help the reader to bettervisual the mesh size, herein the nominal side length of the mesh openingis given parenthetically in microns following the mesh size value.Powder passing through a particular mesh size mesh is said to have thatmesh size. For example, powder passing through a 100 mesh size mesh issaid to be 100 mesh (150 micron) powder. This may also be expressed byplacing a minus sign (−) before the mesh size number. For example, a−100 mesh (150 micron) powder will pass through a 100 mesh (150 micron)mesh. A plus (+) sign placed before the mesh size number is used toindicate that the powder is too coarse to pass through a mesh of thatmesh size. For example, a +100 mesh (150 micron) powder does not passthrough a 100 mesh (150 micron) mesh. Sometimes two mesh sizes givenside by side are used to better describe the particle size of a powder.Under this convention, a minus sign (−) is placed before the first meshsize number (and the word “mesh” beside this number is omitted) toindicate that the powder is small enough to pass through a mesh havingthat mesh size, and a positive sign (+) is placed before the second meshsize to indicate that the powder is too coarse to pass through a meshhaving that mesh size. Thus, a powder sample described as −100 (150micron) +325 mesh (45 micron) is fine enough to pass through a 100 meshscreen and too coarse to pass through a 325 mesh (45 micron) mesh.

Subterranean Drill Bits

Referring to FIG. 1, there is illustrated a schematic of an assembly 10used to manufacture a subterranean drill bit in accordance with anembodiment of the present invention. The drill bit has a shank 24.Cutter elements, such as discrete cutting elements 20, are bonded to theresultant drill bit by way of the metal matrix of the drill bit body.Although the method by which a drill bit shank is affixed to a drillline may vary, one common method is to provide threads on the shank sothat the shank threadedly engages a threaded bore in the drill line.Another way is to weld the shank to the drill line.

The assembly 10 includes a graphite mold 11 having a bottom wall 12 andan upstanding wall 14. The mold 11 defines a volume therein. Theassembly 10 further includes a top member 16 to close the opening of themold 11. The use of the top member 16 is optional depending upon thedegree of atmospheric control one desires to have over the contents ofthe mold 11 during thermal processing.

The steel shank 24 is positioned within the mold 11 before the matrixpowder mixture 22 is poured therein. A portion of the steel shank 24 iswithin the matrix powder mixture 22 and another portion of the steelshank 24 is outside of the matrix powder mixture 22. The shank 24 hasthreads 25 at one end thereof, and grooves 25A at the other end thereof.

A plurality of discrete cutting elements 20 are positioned to extendinto the bottom and upright mold walls 12, 14 so as to be at selectedpositions on the surface of the resultant drill bit. The matrix powdermixture 22 is poured into the mold 11 so as to surround the portions ofthe cutting elements 20 which extend into the cavity of the mold 11. Itis to be understood that in addition to or instead of setting thecutting elements 20 into the walls of the mold 11, cutting elements 20may be mixed in with the matrix powder mixture 22 in amounts up to about20 volume percent. The composition of the matrix powder mixture 22 isdiscussed later herein.

After the cutting elements 20 have been set and the matrix powdermixture 22 has been poured into the mold 11, a solid infiltrant 26 ispositioned above the matrix powder mixture 22. The top member 16 isthen, optionally, positioned to close the opening of the mold 11. Theassembly 10 is then placed into a furnace and heated to an elevatedtemperature so that the infiltrant 26 melts and infiltrates throughoutthe matrix powder mixture 22. The furnace atmosphere is selected to becompatible with the components of the assembly 10 and typicallycomprises one or more of nitrogen, hydrogen, argon, and air. Theassembly 10 is then cooled to solidify the infiltrant 26. The solidifiedinfiltrant 26 bonds together the matrix powder mixture 22, the cuttingelements 20, and the steel shank 24 to form a subterranean drill bit.

Referring to FIG. 2, there is illustrated a schematic of an assembly 30used to manufacture a subterranean drill bit in accordance with anotherembodiment of the present invention. The assembly 30 includes a graphitemold 31 having a bottom wall 32 and an upstanding wall 34. The mold 31defines a volume therein. The assembly 31 further includes a top member36 to close off the opening of the mold 31. The use of the top member 36is optional depending upon the degree of atmospheric control one desiresto have over the contents of the mold 31 during thermal processing.

A steel shank 42 is positioned within the mold 31 before a matrix powdermixture 40 is poured therein. A portion of the steel shank 42 is withinthe matrix powder mixture 40 and another portion of the steel shank 42is outside of the matrix powder mixture 40. The shank 42 has grooves 43at the end that is within the matrix powder mixture 40.

A plurality of graphite blanks 38 are positioned along the bottom andupright mold walls 32, 34 so as to be at selected positions on thesurface of the resultant drill bit. The matrix powder mixture 40 ispoured into the mold 31 so as to surround the portions of the graphiteblanks 38 which extend into the cavity of the mold 31. The compositionof the matrix powder mixture 40 is discussed later herein.

After the graphite blanks 38 have been set and the matrix powder mixture40 has been poured into the mold 31, a solid infiltrant 44 is positionedabove the matrix powder mixture 40. The top member 36 is then,optionally, positioned to close the opening of the mold 31. The assembly30 is then placed into a furnace and heated to an elevated temperatureso that the infiltrant 44 melts and infiltrates throughout the matrixpowder mixture 40. The furnace atmosphere is selected to be compatiblewith the components of the assembly 30 and typically comprises one ormore of nitrogen, hydrogen, argon, and air. The assembly 30 is thencooled to solidify the infiltrant 44. The solidified infiltrant 44 bondstogether the matrix powder mixture 40, the graphite blanks 38, and thesteel shank 42. The graphite blanks 38 are removed from the bonded mass.Cutting elements, such as diamond composite inserts, are brazed into therecesses left by the removal of the graphite blanks 38 to form asubterranean drill bit.

Referring to FIG. 3, there is shown a subterranean drill bit 50according to an embodiment of the present invention. The drill bit 50may be made from a process similar to that described above with regardto FIG. 1. The forward facing surface 52 of the bit body 54 of the drillbit 50 contains cutting elements 56 extending from the infiltrated metalmatrix 58 which resulted from the freezing of an infiltrant throughout amatrix powder mixture.

Referring to FIG. 3A, there is shown a subterranean drill bit 70according to another embodiment of the present invention. The drill bit70 has a bit body 72 and cutting elements 74. The bit body 72 comprisesan infiltrated metal matrix. The cutting elements 74 are brazed to thebit body 72.

It is to be understood that the subterranean drill bits according to thepresent invention are not limited to the geometric designs described inthe foregoing embodiments. Rather, they include all subterranean drillbits having at least one cutting element carried by a bit body in whichthe bit body comprises an infiltrated metal matrix comprising aninfiltrant and a matrix powder mixture, in which the matrix powdermixture comprises (a) about 30 to about 90 weight percent of a firstcomponent powder consisting of particles of cast tungsten carbide of −30(600 micron) +140 (106 micron) in particle size; (b) about 10 to about70 weight percent of a second component powder consisting of particlesof at least one selected from the group consisting of macrocrystallinetungsten carbide, carburized tungsten carbide, and cemented tungstencarbide; and (c) up to about 12 weight percent of a third componentpowder consisting of particles of at least one selected from the groupconsisting of transition metals, main group metals, and alloys andcombinations thereof, wherein the matrix powder mixture containssubstantially no particles of the first component powder of −140 mesh(106 micron) in particle size and particles of the first componentpowder having a particle size of +100 mesh (150 microns) account for atleast 15 weight percent of the matrix powder mixture.

Cutting Element

Each subterranean drill bit according to the present invention has oneor more cutting elements. The cutting elements are preferably naturaldiamond, polycrystalline diamond sintered to cemented carbide, thermallystable polycrystalline diamond, or a hot pressed metal matrix composite,but can be any suitable hard material known in the art. The size andconfiguration of each the cutting element is selected to be appropriatefor the purpose and the conditions under which it is to be used.

The manner in which the bit body carries an individual cutting elementdepends on the design of the particular drill bit and the design of theparticular cutting element For example, cutting elements may be carrieddirectly by the bit body, e.g., by imbedding the cutting elements in theinfiltrated metal matrix of the bit body or brazing them to the bitbody. Alternatively, the cutting elements may be carried indirectly bythe bit body, e.g., by affixing the cutting elements to blades whichthemselves are affixed to the bit body. For example, U.S. PatentApplication Publication No. 2008/0289880 A1 of Majagi et al., which isassigned to the assignee of the present patent application, describes abit body carrying cutting elements which are affixed to blades, whichare, in turn, affixed to the bit body.

Any technique or method known in the art may be used for affixingindividual cutting elements and/or blades having cutting elements to thedrill bit body, including brazing techniques, infiltration techniques,press fitting techniques, shrink fitting techniques, and weldingtechniques.

Infiltrated Metal Matrix

The infiltrated metal matrixes of embodiments of the present inventioncomprise (i) an infiltrant, and (ii) a matrix powder mixture.

(i) Infiltrants

All infiltrants known in the art of making infiltrated metal matrixpowder subterranean drill bits and similar wear resistant elements maybe used in embodiments of the present invention. Examples of infiltrantsinclude metals and alloys comprising one or more transition metalelement and main group element. Copper, nickel, iron, and cobalt may beused as the major constituent of the infiltrant and elements such asaluminum, manganese, chromium, zinc, tin, silicon, silver, boron, andlead may be minor constituents.

Preferred infiltrants are copper-based alloys containing nickel andmanganese, and optionally tin and or lead. Particularly preferredinfiltrants of this type are those which are disclosed in U.S. PatentApplication Publication No. 2008/0206585 A1 of Deng et al. Anotherparticularly preferred infiltrant is the alloy that is available underthe trade name MACROFIL 53 from the assignee of this application,Kennametal Inc. of Latrobe, Pa. 15650 US and under the trade name VIRGINbinder 453 D from Belmont Metals Inc, 330 Belmont Avenue, Brooklyn, N.Y.11207 US. This infiltrant has a nominal composition (in weight percent)of 53.0 percent copper, 24.0 percent manganese, 15.0 percent nickel, and8.0 percent zinc. Another particularly preferred infiltrant is availableunder the trade name MACROFIL 65 from the assignee of this application.This infiltrant has a nominal composition (in weight percent) of 65percent copper, 15 percent nickel, and 20 percent zinc. Anotherpreferred infiltrant has a nominal composition (in weight percent) ofless than 0.2 percent silicon, less than 0.2 percent boron, up to 35percent nickel, 5−35 percent manganese, up to 15 percent zinc, and thebalance copper.

For any particular embodiment of the present invention, the type andamount of the infiltrant is selected so that it is compatible with theother components of the subterranean drill bit with which it is to be inoperational contact. It is also selected so as to provide the drill bitwith the desired levels of strength, toughness, and durability. Theamount of infiltrant is selected so that there is sufficient infiltrantto completely infiltrate the matrix powder mixture. Typically, theinfiltrant makes up between about 20 and 40 volume percent of theinfiltrated metal matrix.

(ii) Matrix Powder Mixtures

The matrix powder mixtures of the embodiments of the present inventioncomprise (a) about 30 to 90 weight percent of a first component powder,(b) about 10 to 70 weight percent of a second component powder, and (c)up to about 12 weight percent of a third component powder. The matrixpowder mixtures are made by blending the component powders together toform a homogeneous mixture.

(ii)(a) First Component Powder

The first component powder consists of cast tungsten carbide powderwhich has a particle size of no smaller than 140 mesh (106 micron). Thecast tungsten carbide provides the resultant drill bit with good erosionresistance. Cast tungsten carbide consists of an approximately eutectoidcomposition of tungsten and carbon having a rapidly solidifiedthermodynamically nonequilibrium microstructure consisting of anintimate mixture of tungsten carbide (WC) and ditungsten carbide (W₂C).The carbon content of cast tungsten carbide is typically in the range ofbetween about 3.7 to 4.2 weight percent.

Cast tungsten carbide powder is available in two forms, crushed andspherical. Although either form may be used with the present invention,the crushed form is preferred because it costs significantly less and ismuch less brittle than the spherical form.

The particle sizes of the cast tungsten carbide powder used in thematrix powder mixtures of embodiments of the present invention are −30(600 micron) +140 mesh (106 micron) with substantially no cast tungstencarbide powder of less than 140 mesh (106 micron) and with at least 15weight percent of the matrix powder mixture weight consisting of +100mesh (150 micron) cast tungsten carbide powder. The phrase“substantially no cast carbide smaller than X mesh” is to be construedto mean that no more than about 10 weight percent of the cast tungstencarbide powder is to be smaller than the indicated mesh size. Thus, inaccordance with the present invention, no more than 10 weight percent ofthe cast tungsten carbide powder present in the matrix powder mixture issmaller than −140 mesh (106 micron) mesh.

The present invention eliminates substantially all fine cast tungstencarbide particles from the matrix powder mixture, because cast tungstencarbide particles of this size are less thermally stable than aresimilar size particles of other forms of tungsten carbide, due to thenonequilibrium microstructure of the cast tungsten carbide. The presentinvention also limits the maximum particle size of cast tungsten carbideparticles so as to avoid compromising the strength and toughness of theinfiltrated metal matrix. Accordingly, the particle size of the casttungsten carbide powder preferably is −30 (600 micron) +140 mesh (106micron), and more preferably is −40 (425 micron) +140 mesh (106 micron),and most preferably is −60 (250 micron) +140 mesh (106 micron).

The amount of the first component powder in the matrix powder mixtureranges from about 30 to about 90 weight percent. The higher amountsresult in more erosion resistance and the lower amounts in more strengthand toughness for the resultant infiltrated metal matrix. Preferably,the amount of the first component powder in the matrix powder mixture isat least about 50 weight percent, and is more preferably at least about60 weight percent.

(ii)(b) Second Component Powder

The second component powder of the matrix powder mixture of embodimentsof the present invention consists of particles selected from at leastone of the group consisting macrocrystalline tungsten carbide,carburized tungsten carbide, and cemented tungsten carbide. The role ofthe second component powder is to enhance the thermal stability,strength, and toughness of the resultant infiltrated metal matrix.

Macrocrystalline tungsten carbide is essentially stoichiometric tungstencarbide (WC) which is, for the most part, in the form of singlecrystals. Some large crystals of macrocrystalline tungsten carbide arebicrystals. U.S. Pat. No. 3,379,503 to McKenna and U.S. Pat. No.4,834,963 to Terry et al., both of which are assigned to the assignee ofthe present patent application, disclose methods of makingmacrocrystalline tungsten carbide.

Carburized tungsten carbide is a type of tungsten carbide that is madeby solid state diffusing carbon into tungsten particles at hightemperatures in a protective atmosphere.

Cemented tungsten carbide powder is also sometimes known as sinteredcemented tungsten carbide. Cemented tungsten carbide consists oftungsten carbide particles bonded together by a binder phase comprisingat least one of cobalt and nickel. Cemented tungsten carbide powder isavailable in two forms, crushed and pelletized (also known asspherical), either or both of which are suitable for use in the secondcomponent powder of the matrix powder mixture.

The particle size of the second component powder is selected so that thesecond component powder particles fit in among the first componentpowder particles in a manner so as to enhance the thermal stability,toughness, and strength of the resultant infiltrated metal matrix. Somepreferred particle sizes of the second component powder are (a) −170mesh (90 micron), (b) −230 mesh (63 micron), and (c) −325 mesh (45micron). In some preferred embodiments, the second component powdercontains substantially no particles −625 mesh (20 micron) in particlesize.

The amount of the second component powder in the matrix mixture rangesfrom about 10 to about 70 weight percent. The higher amounts result inmore toughness and strength and the lower amounts in more erosionresistance in the resultant infiltrated metal matrix. Preferably, therelative amounts of the first and second component powders are selectedso that the ratio of the weight of the first component powder to that ofthe second component powder is in the range of from about 30:70 to about85:15.

(ii)(c) Third Component Powder

The third component powder of the matrix powder mixture is a metalpowder. The metal powder consists of at least one selected from thegroup consisting of the transition metals, main group metals, andcombinations and alloys thereof. The metal powder is selected to aid inthe infiltration of the matrix powder mixture by the infiltrant.Examples of preferred metal powders are nickel, iron, and 4600 gradesteel. The 4600 grade steel has a nominal composition (in weightpercent) of 1.57 percent nickel, 0.38 percent manganese, 0.32 percentsilicon, 0.29 percent molybdenum, 0.06 percent carbon, and the balanceiron.

The particle size of the third component powder is selected so that itblends well into the metal powder mixture. Preferably, the particle sizeof the third component is −230 mesh (63 micron).

The amount of the third component in the matrix powder mixture is in therange of about 0 to about 12 weight percent. Preferably, the amount ofthe third component powder is in the range of about 1 to about 4 weightpercent.

EXAMPLES Examples 1-7

For each example, a matrix powder mixture in accordance with anembodiment of the present invention was prepared by blending togetherinto a uniform mixture the component powders listed in Table 1. Theseexamples are identified in Tables 1 and 3 by the designations Ex. 1through Ex. 7. The first component powder (“component powder 1”)consisted of crushed cast tungsten carbide. The second component powder(“component powder 2”) consisted of macrocrystalline tungsten carbide.The type of the third component powder (“component powder 3”) used ineach example is given in Table 1. For each example, the matrix powdermixture was placed into a graphite mold and subsequently infiltratedwith MACROFIL 53 to create an infiltrated metal matrix.

A photomicrograph of the microstructure of the Example 1 infiltratedmetal matrix appears in FIG. 4. The two phase microstructure of thecrushed cast tungsten carbide particles of component powder 1, e.g.,particle 60, distinguish those particles from the macrocrystallinetungsten carbide particles of component powder 2, e.g., particle 62,which have a single phase microstructure. The binding material 64 thatsurrounds the crushed cast tungsten carbide particles and themacrocrystalline tungsten carbide particles consists of the MACROFIL 53infiltrant in combination with the nickel powder of the third componentpowder.

TABLE 1 Examples of Matrix Powder Mixtures of the Present InventionComponent Component Component Example Powder 1 Powder 2 Powder 3 ID wt.% mesh size wt. % mesh size wt % type Ex. 1 23 −60 + 80 25  −80 + 325 4nickel 23 −80 + 120 25 −325 Ex. 2 38 −60 + 80 20 −325 4 nickel 38 −80 +140 Ex. 3 10 −60 + 80 43 −120 + 325 2 nickel 20 −80 + 120 25 −325 Ex. 420 −60 + 80 25 −120 + 325 2 nickel 28 −80 + 120 25 −325 Ex. 5 23 −60 +80 25 −120 + 325 2 nickel 25 −80 + 120 25 −325 Ex. 6 30 −60 + 80 23 −3252 nickel 45 −80 + 140 Ex. 7 30 −60 + 80 15 −230 + 325 2 nickel 45 −80 +140 8 −325

Comparative Samples 1-4

For each comparative sample, a matrix powder mixture was prepared byblending together into a uniform mixture the components listed in Table2. The comparative samples are identified in Tables 2 and 3 by thedesignations Comp. 1 through Comp. 4. The first component powder(“component powder 1”) consisted of crushed cast tungsten carbide. Thesecond component powder (“component powder 2”) consisted ofmacrocrystalline tungsten carbide. The type of the third componentpowder (“component powder 3”) used in each example is given in Table 2.For each comparative sample, the matrix powder mixture was placed into agraphite mold and subsequently infiltrated with MACROFIL 53 to create aninfiltrated metal matrix.

TABLE 2 Comparative Sample Matrix Powder Mixtures Component ComponentComponent Comparative Powder 1 Powder 2 Powder 3 Sample ID wt. % meshsize wt. % mesh size wt % type Comp. 1 31 −325 67 −80 + 325 1 iron 14600 Comp. 2 15 −325 83 −80 + 325 2 nickel Comp. 3 20 −80 + 325 41 −80 +325 4 nickel 10 −325 25 −325 Comp. 4 20 −60 + 80  54 −80 + 325 1 Fe 24−325 1 4600

Properties

Appropriate size specimens of each of the Example 1-7 infiltrated metalmatrices materials and of each of the Comparative Samples 1-4infiltrated metal matrices were used for measuring the hardness,transverse rupture strength, toughness, abrasion [,] resistance, anderosion resistance. The results of the measurements are summarized inTable 3.

The hardness was measured on the Rockwell C hardness scale in accordancewith ASTM Standard B347-85. Higher values mean indicate greaterhardness. The transverse rupture strength was measured by a three-pointbending test using infiltrated matrix pins of 0.5 inch (1.27 cm)diameter and 3 inch (7.62 cm) length. Higher values indicate higherstrength. The toughness was measured using an impacting test modifiedafter ASTM E23. Higher values indicate greater toughness. The wearresistance was measured in accordance with ASTM Standard B611. Highervalues indicate better wear resistance. The abrasion resistance wasmeasured in accordance with ASTM Standard G65. Lower values indicatebetter resistance to abrasion wear. The erosion resistance was measuredin accordance with ASTM Standard G76. A lower erosion factor valueindicates better resistance to erosion.

The test results show that examples of the infiltrated metal matrixes ofthe present invention are generally harder and are more resistant towear, abrasion, and erosion than are those of the comparative sampleswhile having comparable levels of strength and impact resistance. Thisis also illustrated in FIG. 5, which shows a plot of the transverserupture strength versus the erosion resistance data from Table 3,wherein the results of the examples of the present invention areindicated by diamond markers while those of the comparative samples areindicated by square markers.

TABLE 3 Properties Transverse Erosion Rupture Wear Abrasion ResistanceHardness Strength Toughness Resistance Resistance (erosion ID (RockwellC) (ksi) (MPa) (ft-lbs) (joules) (krev/cm³) (mm³) factor value) Ex. 1 5298 676 1.5 2.0 1.4 5.3 7.65 Ex. 2 52 80 552 1.5 2.0 1.4 8.8 4.62 Ex. 340 121 834 2.6 3.5 0.8 8.3 11.6 Ex. 4 40 107 738 2.3 3.1 1.4 5.3 8.5 Ex.5 41 104 717 2.5 3.4 0.9 5.0 8.9 Ex. 6 40 99 683 2.0 2.7 0.93 10.1 5.1Ex. 7 41 105 724 2.2 3.0 1.0 10.1 5.4 Comp. 1 33 116 800 2.6 3.5 0.65 1524.0 Comp. 2 38 117 807 2.4 3.3 0.81 10 24.34 Comp. 3 48 123 848 2.8 3.81.0 6.3 14.87 Comp. 4 30 111 765 2.5 3.4 0.78 7.3 18.78

While only a few embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art that manychanges and modifications may be made thereunto without departing fromthe spirit and scope of the present invention as described in thefollowing claims. All patent applications, patents, and all otherpublications referenced herein are incorporated herein in theirentireties to the full extent permitted by law.

1. A subterranean drill bit comprising: (a) at least one cuttingelement, and (b) a bit body having an infiltrated metal matrix, whereinthe infiltrated metal matrix comprises: (i) an infiltrant, and (ii) amatrix powder mixture comprising: (A) about 30 to about 90 weightpercent of a first component powder, the first component powderconsisting of particles of cast tungsten carbide of −30 (600 micron)+140 (106 micron) in particle size; (B) about 10 to about 70 weightpercent of a second component powder, the second component powderconsisting of particles of at least one selected from the groupconsisting of macrocrystalline tungsten carbide, carburized tungstencarbide, and cemented tungsten carbide; and (C) up to about 12 weightpercent of a third component powder, the third component powderconsisting of particles of at least one selected from the groupconsisting of transition metals, main group metals, and alloys andcombinations thereof; wherein the bit body carries the cutting elementand the matrix powder mixture contains substantially no particles of thefirst component powder of −140 mesh (106 micron) in particle size andparticles of the first component powder having a particle size of +100mesh (150 microns) account for at least 15 weight percent of the matrixpowder mixture.
 2. The subterranean drill bit of claim 1, wherein thecutting element comprises at least one selected from the groupconsisting of polycrystalline diamond, natural diamond, and thermallystable polycrystalline diamond.
 3. The subterranean drill bit of claim1, wherein the first component powder has a particle size range selectedfrom the group consisting of −40 (425 micron) +140 mesh (106 micron) and−60 (250 micron) +140 mesh (106 micron).
 4. The subterranean drill bitof claim 1, wherein the second component powder particle size isselected from the group consisting of −80 mesh (180 micron), −170 mesh(90 micron), and −325 mesh (45 micron).
 5. The subterranean drill bit ofclaim 1, wherein the weight ratio of the first component powder to thatof the second component powder is in the range of from about 30:70 toabout 85:15.
 6. The subterranean drill bit of claim 1, wherein thematrix powder mixture contains substantially no particles of the secondcomponent powder of −625 mesh (20 micron) in particle size.
 7. Thesubterranean drill bit of claim 1, wherein the third component powderincludes at least one selected from the group consisting of nickel,iron, copper, steel, and alloys and combinations thereof.
 8. Thesubterranean drill bit of claim 1, wherein the matrix powder mixturecomprises about 50 to about 90 weight of the first component powder,about 9 to about 50 weight percent of the second component powder, andup to about 10 weight percent of the third component powder.
 9. Thesubterranean drill bit of claim 1, wherein the matrix powder mixturecomprises about 60 to about 90 weight percent of the first componentpowder and about 9 to about 40 weight percent of the second componentpowder.
 10. A matrix powder mixture comprising: a) about 30 to about 90weight percent of a first component powder, the first component powderconsisting of particles of cast tungsten carbide of −30 (600 micron)+140 (106 micron) in particle size; b) about 10 to about 70 weightpercent of a second component powder, the second component powderconsisting of particles of at least one selected from the groupconsisting of macrocrystalline tungsten carbide, carburized tungstencarbide, and cemented tungsten carbide; and c) up to about 12 weightpercent of a third component powder, the third component powderconsisting of particles of at least one selected from the groupconsisting of transition metals, main group metals, and alloys andcombinations thereof; wherein the matrix powder mixture containssubstantially no particles of the first component powder of −140 mesh(106 micron) in particle size and particles of the first componentpowder having a particle size of +100 mesh (150 microns) account for atleast 15 weight percent of the matrix powder mixture.
 11. The matrixpowder mixture of claim 10, wherein the first component powder has aparticle size range selected from the group consisting of −40 (425micron) +140 mesh (106 micron) and −60 (250 micron) +140 mesh (106micron).
 12. The matrix powder mixture of claim 10, wherein the secondcomponent powder particle size is selected from the group consisting of−80 mesh (180 micron), −170 mesh (90 micron), and −325 mesh (45 micron).13. The matrix powder mixture of claim 10, wherein the weight ratio ofthe first component powder to that of the second component powder is inthe range of from about 30:70 to about 85:15.
 14. The matrix powdermixture of claim 10, wherein the matrix powder mixture containssubstantially no particles of the second component powder of −625 mesh(20 micron) in particle size.
 15. The matrix powder mixture of claim 10,wherein the third component powder includes at least one selected fromthe group consisting of nickel, iron, copper, steel, and alloys andcombinations thereof.
 16. The matrix powder mixture of claim 10, whereinthe matrix powder mixture comprises about 50 to about 90 weight of thefirst component powder, about 9 to about 50 weight percent of the secondcomponent powder, and up to about 10 weight percent of the thirdcomponent powder.
 17. The matrix powder mixture of claim 10, wherein thematrix powder mixture comprises about 60 to about 90 weight percent ofthe first component powder and about 9 to about 40 weight percent of thesecond component powder.
 18. A method of making a subterranean drill bitcomprising the steps of: a) providing a matrix powder mixturecomprising: (A) about 30 to about 90 weight percent of a first componentpowder, the first component powder consisting of particles of casttungsten carbide of −30 (600 micron) +140 (106 micron) in particle size;(B) about 10 to about 70 weight percent of a second component powder,the second component powder consisting of particles of at least oneselected from the group consisting of macrocrystalline tungsten carbide,carburized tungsten carbide, and cemented tungsten carbide; and (C) upto about 12 weight percent of a third component powder, the thirdcomponent powder consisting of particles of at least one selected fromthe group consisting of transition metals, main group metals, and alloysand combinations thereof; wherein the matrix powder mixture containssubstantially no particles of the first component powder of −140 mesh(106 micron) in particle size and particles of the first componentpowder having a particle size of +100 mesh (150 microns) account for atleast 15 weight percent of the matrix powder mixture; c) confining thematrix powder mixture within a graphite mold; d) infiltrating aninfiltrant into the confined matrix powder mixture to form a bit body;e) fixing at least one cutting element to the bit body.
 19. The methodof claim 18, wherein step (e) includes attaching the cutting element toa wall of the graphite mold prior to step (b).
 20. The method of claim18, wherein step (e) includes attaching the cutting element to the bitbody after step (d).